24months later still no refund processed

i opened a contract April 2014 for a broadband Internet service billed at R137.50 monthly for 24 months however i was over billed by R656.05 of which i reported to your offices and was advised to bring my bank statement showing the debit, i did that and was told it has been logged got an sms with a reference number but the money was never transferred back to my account no did telkom stop billing me monthly!. i have had other complaints in the mean time as i was getting no network coverage and that was also logged but nothing happened. i have recently submitted a contract cancellation form dated 06/04/2016 and advised the agent that my money is still not refunded they logged it again and advised me of 10 working days that has also come & gone with nothing done. it's been 2 years of bad service being billed for services that are not rendered and Telkom still owing me R656.05 i now need to know what more should i do to get my money from your company and never have to deal with you ever again!!!!!! case number given is ***5